The invention relates to a vehicle seat for an automotive vehicle, wherein the vehicle seat has a seat pan and a seat back, said seat back being provided with a) a seat back carrier, b) a padding body arranged on said seat back carrier and c) a headrest fastened on said seat back carrier.
When a passenger is sitting in a normal posture, its back rests on the padding body. The head of a passenger is generally located somewhat in front of a headrest cushion of the headrest, the distance between head and cushion typically amounting to several centimeters. Irrespective of the exact dimension of this distance however, a clear space intervenes between the head of many passengers and the headrest cushion of the headrest.
A distance between the headrest cushion and the head of a passenger however has adverse consequences in the event of a rear crash of the vehicle. If for example another vehicle collides into the back of the considered automotive vehicle, the automotive vehicle in question is pushed forward while the passenger in the first place remains still as an inert mass. As a result, the padding body moves toward the back of the passenger together with the headrest carried by the seat back carrier. Consequently, the head of the passenger moves backward until it gets in touch with the headrest cushion. This specific movement often causes ailments or even injuries like for example a so-called whiplash.
It has already been tried to design vehicle seats in such a way that the headrest moves forward in the event of a rear crash. These solutions do not always lead to favorable results.
On the basis of these premises, the object of the present invention is to develop a vehicle seat of the type mentioned above in such a manner that, in the event of a rear crash, a rearward movement of the head relative to the back is possibly avoided and that even in case the head is located at some distance from the headrest cushion of the headrest, head and back are almost simultaneously intercepted in case of acceleration due to an accident, without the head being moved rearward.
Footing on the vehicle seat of the type mentioned above, the solution of this object is to, on one side, provide an upper shoulder area of the padding body, which comes next to the headrest, with a normal disposition to yield to the load of a passenger""s back in the case of a normal automotive vehicle, this disposition to yield increasing considerably on the other side in case of an acceleration of the automotive vehicle brought about by an accident and exceeding a threshold value, so that the thickness of the shoulder area is considerably smaller under the load of a passenger""s back than when it has its normal disposition to yield.
In the event of a rear crash and in accordance with the invention, the harmful effect of a clear space between the head of a passenger and the headrest cushion is prevented by the fact that the upper area of the padding body becomes very soft in case of an accident, so that the back may immerse more deeply into the seat back and that it is only intercepted when the head comes to lie on the headrest cushion. Accordingly, at least the upper area of the padding body has two different dispositions to yield into which it may be brought on purpose. In the normal condition of the automotive vehicle, this upper area, which is also called shoulder area, has a resilience that is standard for use. This resilience complies with the padding quality of standard vehicle seats. In the event of a rear crash, the disposition to yield is abruptly altered, the shoulder area becomes very soft, under the load of a passenger the thickness of the shoulder area may now be considerably reduced relative to its normal disposition to yield. Thus, the back of a passenger may now move farther to the back toward the seat back carrier. If the additional path the back has now at its disposal thanks to the now soft shoulder area equals the distance between head and headrest cushion that was given before the accident occurred, no relative motion between head and trunk takes place, so that a whiplash of the head rearward does not occur. Said additional path may also be greater than the distance mentioned, it should not be smaller, though. The change in the disposition of the shoulder area to yield only takes place above a threshold value of the acceleration of the automotive vehicle. This threshold value is detected by appropriate means. It may for example be determined by detecting devices as they are used for belt tighteners, air bags and so on. It may also be acquired by the relative motion of the passenger relative to the seat back. In the event of a rear crash, the lower part of the passenger""s back also plunges into the seat back, so that this motion may be used to activate the change in the disposition to yield of the shoulder area.
Experience tells that the clear space between the head and the headrest cushion of a headrest usually amounts to approximately 40 mm. This is the measurement by which the thickness should be reduced by the controlled change in the disposition to yield. When the padding body is switched to its soft condition, the thickness of the shoulder area should at least be reduced by 30, preferably by at least 40 mm compared to the thickness of the padding body in its normal condition.
The shoulder area preferably is provided with a supporting part, which is connected to the seat back carrier and which influences and in particular determines the disposition to yield of the shoulder area. This supporting part has a first, normal condition as long as the threshold value of acceleration due to an accident of the vehicle has not been attained. As soon however as this threshold value is attained and exceeded, the supporting part adopts a second condition. In this second condition, it defines a considerably higher disposition to yield of the shoulder area.
In the preferred embodiment, the supporting part is configured either as a mechanical supporting yoke or as an inflated headrest cushion.
In the first case, the supporting yoke is hinged to the seat back carrier and can be brought from a position, in which it is farther away from the seat back carrier into a position, in which it is nearer to the seat back carrier. As a result, reducing the thickness of the shoulder area thus becomes possible in the event of an accident.
The thickness of the shoulder area is not reduced automatically, but rather by the fact that the passenger moves relative to the seat back.
In a preferred embodiment, an elastic means is provided, which pretensions the supporting part in the first, normal condition. The normal disposition to yield of the shoulder area is determined by this means as well. It is also possible that, in case of an operating error, the supporting part returns to its normal position on its own.
A locking device with a movable locking part is preferably provided, said locking part mechanically securing the supporting part in the first condition. The locking part becomes inefficient and no longer secures the supporting part when the acceleration exceeds the threshold value. The motion of the locking part may be controlled by the means already described herein above, like for example by the trigger unit of an air bag or by a very strong motion of a passenger""s bottom into the seat back.
A decisive advantage of the invention is that the headrest is directly assigned to the seat back carrier and that the forces acting upon the headrest are directly transmitted into the seat back carrier and thus into a seat underframe.